Using FireFox? Then good! The Developer Toolbar for FireFox kicks the shit out of the IE Toolbar. Open: chrispederick.com and download the Web Developer Extension directly from the creator’s site. If you are having problems installing it then read the install documentation.

Once you have it installed:
The Information & Outline Tabs offer much more advanced tools than the IE toolbar. With a few quick clicks you will quickly be able to debug a huge amount of possible site problems ranging from DIV tag placement issues, broken tables, a full document outline, and much more.

Quick jumps to some neat tools:
CSS > Disable For Print (Use this to quickly print blog posts and other pages)
CSS > View CSS (Shows the sites CSS file in a tab)

As for toys, the ruler for FireFox is kick ass! Click the Miscellaneous Tab > Display Ruler. Then click and drag the area you want to get the dimensions for.

Validate and find errors quickly. Open your CSS, RSS feed, or website, in your browser. Click the Tools Tab; here you will be able to Validate sponsor feeds, your CSS files or your websites.

Have fun playing around with the toolbar, it has some amazing features. ~ Enjoy